Operation of pressure stills



July 3, 1928.

E. W. ISOM ET AL OPERATION OF PRESSURE STILLS iiea April 19, 1924 4 Sheets-Sheet 1 WWW W &- 516% 6W1 knmv w A TTORNE Y5 July 3, 1928. 1,676,203

' E. w. ISOM ET AL OPERATION OF PRESSURE STILLS Filed April 19, 1924 4 Sheets-Sheet 2 2 HYZIQQIEORS a. By 9% F9% A TTORNE Y5 July 3, 1928.

E. W. ISOM ET AL OPERATION OF PRESSURE STILLS Filed April 19, 1924 4 Sheets-Sheet 5 INVENTOR5 6340 9 ATTORNEYS i July 3, 1928.

E. W. [$0M ET AL OPERATION OF PRESSURE STILLS Filed April 19, 1924 4 heets-Sheet 4 A TTORNE Y5 BY 3% 5m fiw, Mv

Patented July 3, 1928.

UNITED STATES PATENT OFFICE.

, EDWARD W. ISOM, OF WINNETKA, ILLINOIS, AND JOHN E. BELL, F BROOKLYN, NEW

YORK, ASSIGNORS TO SINCLAIR REFINING COMPANY, OF CHICAGO, ILLINOIS,

CORPORATION OF MAINE.

OPERATION OF PRESSURE STILLS.

Application file d April 19,

This invention relates to improvements in the operation of circulatory pressure stills, for cracking petroleum oils and distillates and other heavy hydrocarbons for the production of lighter hydrocarbon oils therei from, in which circulation is effected by positive liquid forcing means such as a pump.

A pressure still typical of this general class is described and illustrated in Patent No. 1,285,200, granted Nov. 19th, 1918, to

the Sinclair Refining Co., on the application of Edward W. Isom. In a still of this type,

the bulk of the oil being processed is contained in a tank exterior to the furnace-by which heat is supplied thereto and the oil is circulated from this tank through a bank of heating tubes in the furnace and back to the tank.

For the most eflicient operation of a still of this type, it is necessary that the oil being treated be quite rapidly circulated and preferably some .positive liquid forcing means such as a pump is employed to effect this circulation. As the temperature of thefcircw lating oil is far above its ignition point and it is commonly under a pressure of four or five atmospheres or even higher, one of the problems encountered is prevention of leakage of the hot inflammable oil. This problem is accentuated by the wide range of temperature to which the pump is subjected, which necessitates the use of large clearances to allow for expansion and contraction due to the temperature changes met with. It is also desirable to protect the mechanical parts of the pump from the hot oil at cracking temperature to as great an extent as possible, and another problem encountered is the lubrication and cooling of those bearings of the pump which are exposed to the circulating hot oil. These and other factors which influence the continuity of operation of the pump are particularly important with respect to circulating pumps employed in circulatory cracking .stills since uninterrupted operation of the pump is necessary to protect the heating elements during the cracking operation.

According to the present invention. cool oil is forced, under pressure in excess of that prevailing inthe still, over and through the pump bearings, which would otherwise be 1924. Serial No. 707,579.

exposed to the circulating hot oil being processed, and into the circulating oil in the pres-' sure still with which it mingles. By forcing cool oil over and through the pump bearings, overheating of the bearings is avoided and the bearings are thoroughly lubricated while the escape of hot oil is prevented. The inflowing cool oil cools the bearings and protects them from the circulating hot oil at cracking temperature, and permits the use of suflicient clearance in the bearings to eliminate sticking or binding of the shafts 1n the bearings, and consequentstoppage of the pump, due to the extreme yariation in temperature to which the pump is subjected. Thorough lubrication of the bearings by the infiowing oil is also promoted by the cooling effect thereof.

In carrying out the method of the present invention, the amount of cool oil forced into the pressure still through the pump bearings may be just sufficient to prevent the outflow of the circulating hot oil, or an additional quantity-of oil may be forced through the bearings securing an increased cooling and lubricating effect. In addition to the oil forced into the circulating hot oil through the pump bearings, a further quantity of cool oil may be supplied to the bearings and circulated thereover to secure an additional cooling effect, and the excess oil which is not forced through the bearings may be introduced into the still at another point or may be allowed to escape through other channels, \Vhere excess cool oilis supplied to the pump bearings, the excess oil may be returned to the supply and recirculated over the bearings, with or without intermediate cooling.

The method of this invention is of special value and application in conjunction with circulatory pressure stills in which circulation is effected by rotary piston pumps. In'

carrying out the invention in conjunction with pumps of this type, a housing is provided about the bearings externally of the pump chamber and the cool oil is forced into this housing by an independent pump, adapted to maintain a pressure higher than that prevailing in the still or in the pump chamher, and the pump bearings and shafts are proportioned so that the shafts fit loosely in the bearings. A thin film of cool oil is thus forced through the bearings exposed to the hot oil at cracking temperature, preventing the escape of hot oil through the loosely fitting bearings and also cooling and lubricating the bearings. Any shafts projecting beyond the external housings, such as the pump drive shaft, pass through .stufiing boxes in the housing. These stuffing boxes are exposed only to cool oil and can be maintained tight with comparative ease. Moreover, any oil escaping through them is cool and below dangerous temperatures.

Vi here rotary piston circulating pumps are operated in accordance with the present invention, the pump chamber and the impellers or pistons are advantageously proportioned so that there is a substantial clearance between all moving parts and bet-ween all moving parts and stationary parts. This clearance may be to 3 more or less between the pump pistons and the side of the casing or chamber, and somewhat less between the pistons and the end of the chamber, The provision of such clearances largely eliminates or reduces any necessity for dismantling and cleaning out carbon which tends to deposit on all parts of the pump exposed to oil at cracking temperature circulating through the still and which causes the pump to bind or freeze so that it cannot be turned over. l/Vhen first installed, a pump with such clearances is ineflicient on account of the amount of leakage which occurs, but in the course of operation and in pumping hot oil containing carbon, a part of the carbon deposits within the pump, and if the pump is kept in continuous operation, the carbon so deposited on surfaces moving relatively to each other is ground until it effects a satisfactory seal. As there is a continual grinding action during all the time the pump is in operation, the thickness of this carbon deposit determines the resistance or friction due to this form of seal. lVhen the carbon layer is very thin, the shearing action necessary for grinding off the precipitate is excessive and may be reduced by increasing the thickness by increasing the clearance. lVhere the circulating oil passing through the pump is relatively free from carbon, the use of clearances materially larger than required to accommodate variations due to temperature change is not desirable.

The invention will be further described in connection with the accompanying drawings illustrating apparatus adapted for practice of the process of the invention, but it will be understood that the invention is illustrated thereby, not limited thereto. In the accompanying drawings:

Fig. 1 is a vertical section of a rotary piston pinup adapted for use in carrying out the invention;

Fig. 2 is a transverse section of the pump taken on the line 2-2 of Fig. 1;

Fig. 3 is a transverse section of the pump taken on the line 33 of Fig. 1;

Fig. 4 is an end elevation partly in section of the pump; and, 7

Figs. 5, 6 and 7 diagrammatically repre sent in side elevation and partly in section three still systems for carrying out the process of the invention.

\Vhile the invention applicable in connection with circulating pumps of different types, it is of particular advantage in connection with circulating pumps of the character illustrated. This pump is of the rotary piston two lobe type.

The pump illustrated in Figs. 1 to 4 comprises a body casting 5 containing the pump chamber 6, the inlet connection 9 and the outlet connection 10. The piston chamber is closed at its ends by end castings 11 and 12. The pump chamber is oblong, as shown in Fig. 2. and is formed with semi-cylindrical ends, the pistons 7 and 8 being arranged to rotate therein in such close relation with each other and with the walls and ends of the body castings as to constantly form a seal between the inlet and outlet sides of the pump chamber 6. The pistons turn oppositely, in the directions indicated by the arrows, each piston at each half revolution shutting oli' a supply of liquid received from the inlet side of the pump between the body of the piston and the corresponding end of the housing and transferring it to the outlet side of the pump. The shafts, 15 and 16, on which the pistons are-mounted, arejournaled in the end castings, 11 and 12, and are provided with gears, 13 and 14: respectively, which intern'lesh so that the pistons are driven in unison. One of the shafts, 16, extends beyond the pump casing providing an extention 17 which may be coupled to any suitable source of power to drive the pump.

Pumps of this general description are well known, but for handling hot oil at cracking temperatures and under pressure, in accordance with the method of this invention, certain modifications are particularly advantageous. For carrying out the process of the present invention, the pump shafts are proportioned to fit loosely in the bearings and provision is made to force relatively cool oil, preferably of the kind being processed, through the bearings into the hot oil within the pump chamber, thus preventing the escape of the hot oil and thoroughly lubricating the bearings and preventing them from becoming unduly heated. The

llO

end castings 11 and 12 are similar in construction and therefore are described together. These end castings comprise a main body portion 18, of suitable dimensions to provide for the bearings of the shafts 15 and 16 which are formed therein, and end flanges 19'and 20 arranged at respective ends of the body portion and c nnected by webs 21, certain of which are shown in section in Fig. 1. The main or body casting of the pump is formed with flanges 25, to which the flanges 1.9 of the end castings are bolted. The body portions of the end castings are formed with suitably spaced bores 22 which receive bushings 23 in which are formed the bearings for the shafts 15 and 16 upon which the rotary pistons are keyed. The fit of the shafts in the bushings is sufficiently free to avoid binding at all times, notwithstanding the wide range of temperature to which the pump is subjected, and to permit the passage of a thin film of oil into the pump chamber about the. shafts. The gears 13 and 14 are mounted on respective shafts beyond one of the end castings and are enclosed in a housing 28, the flange of which is bolted at 29 to the outer flange of the end casting. The shaft 16 by which the pump is driven extends through the housing at 39 where there is provided a packing box 40 containing the packing 41 and receiving the gland 42. Openings 35 and 36 areformed in the end of this housing and receive an inlet pipe 37 and an outlet 38 by which cool oil under pressure may be supplied to and re moved from the housing. The other end casting is provided with a cap or cover plate 26 which is bolted thereto at 27 This cover plate is recessed or chambered at 30 and provided with openings 31 and 32.which receive inlet and outlet pipes 33 and 34 through which cool oil under pressure may be supplied or removed from the chamber 30.

The pressure still illustrated in Figs. 5, 6 and 7 is made up of the bulk supply tank 48, located away from the heating furnace, the vertical-heating tubes 50, arranged in the heating flue in the furnace, and circulating pipes 51, 47 and 49, connecting the lower and upper ends of the vertical tubes, respectively, with the bulk supply tank, and a circulating pump 40 for circulating the oil from the bulk supply tank through the vertical tubes and back to the bulk supply tank. Vapors are discharged from the vapor dome on the bulk supply tank through connection 52. F resh feed oil may be introduced into the still or reflux condensate returned to the still through connection 53 which discharges into the circulating pipe 51. Connection 54 is provided for withdrawing tar from the bulksupply drum 48. The main circulating pump 40 is of the construction illustrated somewhat more in detail in Figs. 1 to 4. The auxiliary pump 44 is adapted to force cool oil from the supply receptacle 46 to the chamber 30 in the cap plate 26 and to the gear housing 28 of the pump 40 under a pressure in excess of that prevailing in the chamber of the pump 40.

In carrying out the method of the invention in pressure stills of the character illustrated, all of the oil supplied to the chamhers about the bearings of the main circulating pump may be forced through the bearings into the pump chamber, and the amount of cool oil forced into the pump chamber through the bearings may be regulated to provide just sufficient inflow of cool oil to prevent the escape of hot oil and to cool and lubricate the bearings, or additional cool oil may be forced in through the hearings to provide an increased cooling and lubricating effect, or for the purpose of introducing fresh feed oil at this pointin excess of that required to cpol and lubricate the bearings and prevent the escape of hot oil. Or only a part of the. oil supplied to the chambers about the pump bearings may be forced through the bearings into the pump chamber, the additional cool oil circulated over the bearings assisting in further cooling the bearings. The additional oil over that amount forced into the cireulating oil through the pump bearings may be returned to the supply receptacle or may be introduced into the still at another point, or may be partly recirculated to the supply receptacle and partly introduced into the still at another point. Where additional oil over that forced in through the bearings is circulated'over the'bearings, the amount of oil forced in through the bearings may also be regulated for the purpose of supplying fresh feed oil at this point or just suflicient oil may be forced in through the hearings to cool and lubricate them and to prevent the escape of hot oil. Fresh feed oil may likewise be independently introduced into the still at other points, for example, into the bulk supply drum, or into a reflux ,tower through which the vapors from the still pass and from which it is returned to the still with the reflux condensate. Still systems adapted to carry out these modifications of the process of the invention are diagrammaticallyrepresented in Figs. 5, 6 and 7.

In carrying out the method of the'invention in connection with the use of a rotary piston pump of the type-illustrated circulatmg, for example, 2000 gallons per-minute of hot oil at a temperature between about 700 F. and 800 F., a flow of about 3 gallons per minute of cool oil, that is oil at about atmospheric temperature, into the pump chamber through the pump bearings is suflicient to prevent the escape of hot oil through the pump bearings and to cool and lubricate the pump bearings. For the purpose of securing an increased cooling effect or of introducing additional fresh feed-oil into the hot circulating oil at this point, the amount of oilforced "in through the pump bearings may be increased to 17 gallons per minute, for example, or more.

In the operation of a still of the construction illustrated in Fig. 7, the main circulating pump 40 is operated to circulate the oil from the drum 48 to and through the heating pipes 50 from which the oil returns tothe drum 48 through pipe 49. The small pump 44 is continuously operated to draw cool oil from the supply tank 46 and force it to the chambers about the bearings of the main circulating pump 40 through connections 55 and 56 and the meter 60 under a pressure in excess of that within the pump chamber. The cool oil supplied to the chambers about the bearings is thus forced through the pump bearings into the main pump chamber where it mingles with the hot oil after having served to prevent the escape of hot oil through the bearings and to lubricate and cool the bearings. Additional oil may be introduced into the lower part of the heating pipes 50 by means of pump 44 through connections 55 and 57 and meter 62, or additional oil may be introduced into the still at some other point through connection 58 and meter 61. For example, additional feed oil may be introduced into the still through connection 53, or the oil discharged through connection 58 may be introduced into the upper part of a reflux tower communicating with the vapor dome on the drum 48 through connection 52, and the reflux condensate and un vaporized feed oil returned to the still through connection 53. The various connections for introducing fresh oil from the receptacle 46 into the still are preferably provided with check valves 59 to prevent return flow and With suitable valves to regulate the flow therethrough. Just suflicient oil may be supplied to the chambers about the bearings of the main pump-4O to prevent the escape of the hot circulating oil through the hearings or an additional amount of oil may be forced in through these bearings either to provide an increased cooling and lubricating effect or for the purpose of introducing additional feed oil into the still at this point. Since all of the oil forced into the chambers about the main pump bearings is forced through the bearings of the pump40 in the still structure illustrated in Fig. 7, the meter 60 will indicate the total amount of fresh oil discharged through the pump bearings into the circulating oil in the still.

In the operation of a still of the constructionillus'trated in Fig. 6, the pump 40 is operated to circulate the oil from and to the drum 48 through the heating pipes 50 in a similar manner. The small pump 44 is operated to force cool oil from the supply tank 46 to the chambers about the bearings of the main circulating pump 40 through connections 56 and meter 60 under a pressure in excess of that Within the pump chamber, and connections 64 are prov "ided to return oil which is circulated over the bearings but not forced in through the hearings to the supply receptacle 46 through the meter 63. Fresh cool oil is thus circulated over and about the pump bearings and part of this circulating cool oil is forced in through the pump bearings into the main pump chamber where it mingles with the circulating hot oil, preventing the escape of the hot oil through the bearings and cooling and thoroughly lubricating the bearings. The additional quantity of oil circulated over and about the bearings provides an increased cooling effect, and by regulating the amount of oil circulated over the pump hearings in excess of that forced through them into the main pump chamber, a regulated and increased cooling of the' bearings of the circulating pump 40 may be secured. The meter 63 indicates the amount of oil circulated over the main pump bearings from and to the supply receptacle 46 and the difference in the reading of the meters 63 and 60 indicates the amount of oil forced into the circulating hot oil through the main pump bearings. An additional quantity of feed oil may be introduced into the still at any other convenient or desirable point from the supply receptable 46 through connection 58 and meter 61,

In the operation of a still of the construction illustrated in Fig. 5, the main pump 40 is operated to circulate the oil from the still proper or vaporizing drum 48 to and through the heating pipes in the furnace from which the oil returns to tank 48 through pipe 49. The small pump 44 is continuously operated to force a circulation of cool oil from supply tank 46 to the chambers about the main pump bearings. A part of this cool oil is forced through the bearings of the shafts fromthe chambers about these hearings into the main pump chamber where it mingles with the hot oil after having served to prevent the escape of the hot oil through the bearings and after having cooled and thoroughly lubricated the latter. The remainder of the oil passes through the pipes 34 and 38 to the connection 47 between the circulating pump and the heater where it mingles with the hot oil passing from the circulating pump to the heater. The flow of oil through SIS the pump bearings into the pump chamber the modifications described in connection with "Figs. 5, 6 and 7, can be combined with particular advantage in semi-continuous cracking operations. In the' operation of a pressure still of the type described in Patent No. 1,285,200, hereinbefore referred to, just sufiicient oil to prevent the outflow of the oil circulating through the main pump may be introduced through the pump bearing's while the still is being brought to cracking conditions of temperature and pressure. Or, particularly during the latter part of the initial period of operation, an additional quantity of oil may be circulated over the pump bearings to secure an increased cooling effect, this additional quantity of oil being returned to the supply receptacle. After the still has been brought to cracking conditions of temperature and pressure, and after distillation has begun, additional fresh feed oil may be introduced through the pump bearings to maintain or assist in maintaining the oil body within the still. During the final period of operation of the still, the amount of oil forced in through the bearings may again be reduced to an amount just sufiicient to prevent the escape of hot oil, either with or without the circulation of additional cool oil over and about the bearings from and to the supply receptacle for securing additional cooling thereof. The method of the inven tion is of special value and application in conjunction with circulatory pressure stills provided with reflux towers in which reflux condensation is regulated by the introduction of fresh feed oil. Regulation of the quantity of oil circulating within the still can be effected independently of the amount of feed oil introduced through the reflux tower by regulation of the amount of fresh feed oil introduced through the pump bearings, or the introduction of fresh feed oil through the reflux tower may be supplemented by the introduction of fresh feed 011 through the circulating pump bearings.

It will thus be seen that the present invention provides an improved method of ope ration of circulatory pressure'stills in which circulation is maintained by pumps where-l pressure stills in which circulation is mainby the bearings of the circulating pump are cooled and vlubricated-and protected from the hot circulating oil crackingtemperature. and under pressure within the pump by forcing cool'oil over and'through the pump bear- 'ings which would otherwise be exposed to the circulating hotoil. It will further beseen that this in'ventionprovides'animproved method of introducingf-resh feed oil I into circulatory crackin stills whereby-the fresh cool oil is'utilize to. cool andv lubricate the bearings of the circulating pump. This application is in part a continuation of an application filed May 12th, 1921, Se-

rial No. 469,036.

We claim: v I I p 1. A method of cooling and lubricating 'the bearings of circulating pumps having drive shafts in loosely fitting bearingshamv v shafts in loosely fitting bearings, which comprises forcing the fresh oil through the pump bearings under pressure in excess of that prevailing in the still into the hot-oil circulating through the'pump. 3. A method of cracking oil, which, comdling hot oil under ulperatmosplieric pr'essure, in circulatory cracking-st1lls,,cons1st1ng prises circulating the oil from and to a bulk supply tank through a heater maintained at x a cracking temperature by and through 'a circulating pump having a drive shaft in loosely fitting bearings while maintaining the oil under superatmospheric pressure, supplying fresh oil to the pump bearings and forcing the fresh oil so supplied into the. 4

hot circulating oil through the pumpbearlngs.

prises circulating the oil from and to a bulk supply tank through a heater maintained. at a cracking temperature by and through a circulating pump having a drive shaft in 4. A method of cracking oil, whichom- I loosely fitting bearings while maintaining the. oil under superatmospheric pressure,- feeding fresh oil to the still and forcing a substantial part of this fresh oil through the pump bearings into the hot circulating oil.

5. In a method of cracking oil in circu latory pressure stills in which fresh oil is introduced into the stills during the cracking operation and in which circulation is effected by pumps having drive shafts in;

loosely fitting bearings, the improvement I which comprisesforcing a substantial part of the fresh oil through-the pump bearings into the hot. oil circulating in thestill.

" 6! A method of cracking oilin circulatory I I tained by pumps having drive shafts in loose fitting bearings, which comprises'heating the the circulating oil in amount su'flic-ient to prevent the outflow of the circulating oil,

and after the oil has attained a cracking ten1-.

erature int oduc ng add ti n f e h feed oil through the pump bearings into the circulating hot oil.

7. A semicontinuous method of cracking oil in circulatory pressure stills in which circulation is maintained by pumps having drive shafts in loose fitting bearings, which comprises heating the oil toand at a cracking temperature under superatmospheric pressure while maintaining circulation, initially forcing cool oil through the circulating pump bearings into the circulating oil in amount sufficient to cool and lubricate the bearings and to prevent the outflow of the circulating oil, after the oil has attained cracking temperature introducing additional fresh feed oil through the pump bearings into the circulating hot oil, and subsequently decreasing the amount of oil introduced through the pump bearings but maintaining the amount suflicient to cool and lubricate the bearings and to prevent the outflow of the circulating oil.

8. The improvement in the cracking of hydrocarbon oil in circulatory pressure stills, which comprises circulating the carbon containing oil by and through a rotary piston circulating pump having a substantial clearance space between the pistons and the Walls of the pump casing, grinding the carbon deposited in the clearance space between the pistons and Walls of the pump chamber to form a seal between said members by rotation of said pistons and maintaining'said seal by continuing the operation of the pump throughout the cracking period.

In testimony whereof We aifix our signatures.

EDWARD W. ISOM. JOHN E. BELL. 

